sedimentary

Tumbled brown jasper / chert

Microcrystalline quartz (SiO₂), commonly called jasper or brown chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, tan, gray, and reddish coloration with a waxy to dull luster. It has cryptocrystalline quartz structure, no visible cleavage, conchoidal fracture, and typically high durability; the rounded shape indicates natural or artificial tumbling.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement fine sediments, often incorporating iron oxides that create brown and red colors. Deposits range from Precambrian to recent ages and occur in sedimentary, volcanic, and hydrothermal settings.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, and lapidary collections; crushed jasper/chert may be used as aggregate or decorative stone.

Geological facts

The specimen’s mottled opaque appearance and conchoidal-looking pits are consistent with jasper or chert, though the image cannot distinguish them confidently. It may also contain minor iron oxides, clay minerals, or fossil remnants.

Field identification & locations

Identify it by testing for glass-scratching hardness, observing opaque microcrystalline texture, and checking for conchoidal fracture; it is commonly found in sedimentary gravels and jasper beds worldwide. Avoid confusing it with brown chalcedony, which is usually more translucent.